The coccidia are intracellular protozoan parasites which are prevalent in all domestic animals as well as in man. They are the cause of coccidiosis, which is characterized by enteritis. Coccidia of the genus Eimeria cause severe intestinal infections in poultry and ruminants (cattle, sheep e.t.c.). In fact, coccidiosis is one of the most-frequently occurring diseases of poultry (see inter alia “Poultry Diseases” by Jordan, F. T. W. and Pattison, M., 4th ed., pp. 261-276, 1996, W. B. Saunders Co. Ltd., London, UK). It deserves mentioning that the annual costs for anticoccidial medication is about £5 million in the UK only. In poultry, most cases of coccidiosis are caused by protozoa belonging to the genus Eimeria, such as e.g. E. maxima, E. tenella, E. acervulina, E. necatrix, E. hagani, E. praecox, E. mitis and E. brunetti. Other examples of infectious Eimeria protozoa are E. gallopavonis, E. meleagrimitis, E. adenoeides, E. meleagridis, E. dispersa, E. innocua, E. subrotunda, E. truncata, E. anseris, E. bovis, E. zurnii, E. alabamansis, E. auburnensis, E. ashsata, E. parva, E. faurei, E. arloingi, E. debliecki and E. spinosa. 
In poultry, e.g. chickens and turkeys, an outbreak of coccidiosis may with little or no forewarning lead to a serious infection, and unless the birds are promptly treated, the result may be a very high mortality. Animals that survive these types of infections are usually of reduced economical value, since they become less efficient in converting feed to weight gain, grow much more slowly than normal animals and frequently appear listless. A similar disease scenario may also occur upon coccidia infection of larger animals, e.g. ruminants and pigs, albeit the problem is in general more severe in poultry.
In the treatment of coccidiosis, a recognized problem is the development of resistance to known anticoccidial agents. This problem has been addressed in numerous publications, such as in Stephen B. et al., Vet. Parasitol., 69(1-2), pp 19-29, 1997. Indeed, there is a strong and ongoing demand in the art for both new and improved antiparasitic compounds, particularly for the treatment of coccidiosis.
As relevant prior art mention can be made of U.S. Pat. No. 5,776,982, EP 0 015 110 and U.S. Pat. No. 4,486,439, which disclose compounds useful for treatment of coccidiosis. However, none of these documents specifically discloses or suggests the compounds of the present invention.